The present invention relates to a method, and a system employing same, enabling one or more equipments set up on board a vehicle to be harmonized in a self-contained manner. In particular, and in a non-limiting manner, the invention applies to aircraft.
It is known that certain equipments loaded on board a vehicle must have a fixed orientation relative to the latter; this is the case in particular for inertial navigation instruments, detection instruments and armaments systems. The collection of these equipments must operate using common reference axes, which requires an initial setting of each of their reference axes. To do this, a reference trihedral is defined for the vehicle, which serves as basis of reference for the orientation of reference trihedrals relating to the various equipments. Such a setting operation is called harmonization or alignment.
Various procedures are known for carrying out this operation.
A first procedure consists in mounting the equipment to be harmonized on a rack comprising a fixed part, integral with the vehicle, and an adjustable part integral with the equipment, the position of this equipment being referenced by optical sighting and modified by reference to another optical measurement appertaining to an already harmonized reference system. This procedure customarily serves for the harmonization of the inertial modules mounted on board aircraft.
Such a procedure is fairly tricky to implement since it requires sighting means external to the vehicle, and, furthermore, it necessitates being able optically to access the equipments to be harmonized, this being a significant constraint in the choice of their location.
This procedure determines the harmonization error angles for each equipment and requires them to be corrected later by a mechanical rotation. By virtue of this, it is lengthy and tricky to implement.
Another procedure consists in using fitment planes produced with the desired accuracy and harmonized, This requires accurately positioning an appliance relative to the vehicle and later making it carry out an accurate machining of the fitment plane, which is thus harmonized. This fitment plane later receives two accurately machined centering pins on which the equipment will be mounted.
This procedure, which uses successive transfers of accuracy of mechanical positioning, is awkward to implement. In particular, it requires as many fitment planes as there are equipments to be installed, and the latter must also have available accurately machined fixing means, this raising the cost.
A more sophisticated procedure, following French Patent 2 610 101, consists in arranging the equipment in a fixed rack and in determining the harmonization error by comparing between an appliance, serving as reference to define the axes of the vehicle, and another appliance temporarily substituted for the equipment to be harmonized. The harmonization error, which is stored in the memory of a computer of the vehicle, serves subsequently for the latter to correct, through calculation, the values output by the equipment. The latter must clearly have an accurate fixing device which is a copy of that of the appliance which has been substituted.
This procedure thus avoids mechanical adjustments, but requires, however, a reproducibility of the fixing means, as well as measurements by optical sighting.
For its part, the U.S. Pat. No. 4,134,681 describes a harmonization procedure using two laser beams, the orientation of each of which is detected by two equipments which define the components of these beams in their characteristic trihedral. A computer receives these data and has available sufficient equations to determine the three angles of error between these two equipments. Since one of these equipments is already harmonized, the calculated error in angle is thus the harmonization error of the other equipment.
Such a procedure thus avoids a mechanical adjustment since the computer will be capable of correcting, through calculation, the data provided by the equipment which is not mechanically harmonized. However, it requires optical measurements and therefore imposes constraints as regards the positioning of the equipments.